1. Field of Invention
This invention relates to piano key mechanisms, and more specifically to improvements in measuring the performance characteristics of key mechanisms of a piano or keyboard.
2. Background Art
As an aid to the following prior art discussion, a brief description of the two basic piano actions follows.
FIGS. 1, 1A, 2 and 2A demonstrate operation of a prior art grand piano action 100. For the purpose of better understanding, with reference to these figures, the following components remain stationary with respect to the piano during a sequence of key depression through hammer strike and return: hammershank flange 134, hammershank flange center pin 136, repetition support center pin 112, key fulcrum 104, key pin 106, drop regulation screw 196, jack let-off button 170 and string 140. With respect to FIGS. 1 and 2, the “back” of the key or action is to the left in the figures. The “front” of the key or action is to the right. Still referring to FIGS. 1 and 1A, the prior art grand piano action 100 is shown in the “at rest” position. Wooden key 102, approximately 15 inches long, is mounted to pivot on felt-covered, wooden fulcrum 104 and brass pin 106 extending through a vertical slot (not visible in the figures) in key 102. Wippen 110 is mounted for rotation about metal center pin (a fixed pivot point) 112. Two levers are mounted to rotate independently within the repetition assembly: an L-shaped jack 120 mounted to rotate about center pin 121, and repetition lever 123 mounted to rotate about center pin 114. Felt hammer 130 is fixedly mounted at the free end of wooden shank 132, and wooden shank 132 is mounted to rotate about center pin 136, held stationary by flange 134. As the hammer 130 is rotated upwardly, it strikes tensioned piano string 140 to create vibration and sound. Affixed to hammershank 132, between hammer 130 and center pin 136, is buckskin covered cylindrical knuckle 150, engaged upon the top end surface 128 of the upper arm 122 of the jack 120. The jack 120 is maintained in the “at rest” position shown in FIGS. 1 and 1A by action of a lower end of return spring 160, which bears against the rear surface 129 of the jack, thus urging it to rotate backward (counter-clockwise in the drawings), about center pin 121, until the felt regulating button 162 (mounted on the upper jack arm 128) is brought into contact with the rigid metal spoon 164 (mounted to wippen 110). The upper end of return spring 160 biases the forward end of repetition lever 123 to rotate upwardly, about center pin 114, until the pad 166, mounted at the front end of repetition lever 123 is brought into contact with the wippen 110.
Also shown in FIG. 1, but left out of FIG. 2 for clarity, is the damper assembly 198. The damper assembly of a piano provides additional resistance to the stroke unless the sustain pedal is depressed. Pressing the pedal disengages the damper lever entirely from the key. All of the Up Weight and Down Weight measurements are done with the damper lever disengaged. All new methods by the present author, designed to replace these old parameters, are also done with no dampers involved.
We refer next to FIGS. 2 and 2A (in which the position of the action 100 in the “at rest” position of FIG. 1A is indicated in dashed line for ease of reference). Upon depression of the key 102 (indicated by arrow 180), wippen 110 is moved upwardly, to rotate (arrow 182) around center pin 112, thereby actuating the various interengaged elements of the repetition assembly (i.e. wippen 110, jack 120, repetition lever 123, spring 160, regulating button 162 and spoon 164) and moving the hammer 130 towards striking engagement with the piano string 140. In particular, movement of the jack 120 urges the knuckle 150 upward and to the left (in the drawings), causing the hammershank 132 to rotate about center pin 136, driving the hammer 130, at the free end of the hammershank, upward and to the left, toward the piano string 140 (arrow 184). During movement of the knuckle 150 upward and to the left, the engagement of the knuckle surface with the top end surface 128 of the jack 120 creates excessive friction, which has the recognized consequence of requiring a pianist to apply additional force in order to achieve the desired key depression. Approximately midway through full depression of the key 102, the outer end of the lower arm 126 of jack 120 is brought into engagement with stationary let off button 170. At this point, a significant “let-off” resistance is encountered, but this is of little consequence when it comes to evaluating the Down Weight and Up Weight of a piano action. When the key nears the bottom of its stroke, the felt pad at the front rail is compressed between the key bottom and the keybed, eventually ending the downstroke.
FIGS. 3 and 4 represent a side view of a typical upright piano action. The majority of a piano key 1 is not shown, along with the fulcrum upon which the key pivots. A downward movement of the piano key 1 causes a capstan screw 22 mounted on key 1 to raise upwardly and engage a cushion 23 of a wippen 24 mounted for pivotal movement about a center pin 25. This causes wippen 24 to be raised, thereby also imparting a corresponding raising of a jack 2, the latter in turn causing a simultaneous thrust of a hammer 3 in the direction of a piano string 4. As key 1 is depressed, string 4 is freed from a damper 5 by the action of a spoon 6, so that once the hammer 3 hits the string 4, the latter will be free to vibrate. A sustain pedal (not shown) independently rotates the damper about its pivot 32, preventing contact from occurring with the spoon 6. An escapement is realized immediately prior to hammer 3 hitting string 4 because a toe 7 of the lower end of jack 2 engages a regulating button 8. This causes jack 2 to rotate clockwise, and a tip 13 at the upper end of jack 2 disengages from a butt 11 of hammer 3, thereby permitting hammer 3 to freely pursue its movement. Once escapement is triggered, key 1 also continues its downward movement independent of hammer 3, until the key bottoms out on the key bed (not shown). When hammer 3 strikes string 4 and is propelled rearwardly, key 1 remains fully depressed and a butt heel 10 mounted on an arm 18 of hammer 3 engages a back check 9 which remains in a raised position. As also shown in FIGS. 3 and 4, damper 5 includes a felt 26 for engaging string 4 and an associated drum block 27 and set screw 28. Damper 5 is mounted on a lever 29 which in turn is mounted to a lever flange 31 for pivotal movement about a center pin 32. Hammer rest 12 includes a felt 34 for engagement by hammer 3 and an associated half blow rest rail 35 and a rest rail 36. Butt heel 10 is provided with an associated butt heel leather 37 and a bridle wire 39. Jack 2 is mounted to wippen 24 by a flange 21 for pivotal movement about a center pin 20. Pivotal movement of jack 2 is biased by a spring 40. Regulating button 8 is mounted to a regulating rail 41 and there is provided a main action rail 42.